Prof. Benny Chefetz

Ongoing Research

Dissolved organic matter fractionation and pollutant interactions in soils irrigated with reclaimed wastewater

PIs: Benny Chefetz, Myrna Simpson (University of Toronto) and Edward G. Gregorich (Agriculture & Agri-Food Canada)


Israel leads the world in recycling wastewater for agricultural use. It is expected that in 2009 reclaimed wastewater may account for >50% of total irrigation water. Introduction of relatively high levels of dissolved organic matter (DOM) and xenobiotics into the environment by this practice may have deleterious effects on the soil physical, chemical and biological properties. Furthermore, the long-term sequestration and transport of the xenobiotics, specifically pharmaceutical compounds (PC), is not well known. Therefore, the focus of this research is to obtain detailed information about the chemical structure and biological nature of the DOM and PCs in reclaimed wastewater, as well as how these compounds interact, individually and in combination, with soil constituents. We hypothesize that the fate of xenobiotics in soils irrigated with reclaimed wastewater is primarily affected by the reactivity and biodegradability of the DOM in soils.

We will conduct fundamental research to characterize the adsorption and fractionation of DOM in soils to elucidate the effects of this fractionation on PC interactions. Recent research suggests that DOM-mineral interactions indirectly govern the fate of environmental contaminants in soil; however, this relationship is poorly understood. Therefore, we plan to apply advanced nuclear magnetic resonance (NMR) techniques to conduct molecular-level characterization of DOM, DOM-mineral interactions, and DOM-PC interactions. The NMR studies will be coupled with macroscopic studies with the overall goal of elucidating DOM fate and its role in the fate of PC in soils. The biodegradability of DOM and the influence of PCs on DOM biodegradation (and vise versa) will be evaluated using laboratory bioassays. The biological response to PCs will be quantified by measuring biogenic gas emissions and soil properties such as substrate utilization efficiency, nitrification potential, microbial biomass, and mineral C and N concentrations.

This research will provide a fundamental understanding of DOM fate and its role in the sequestration of PCs and other organic pollutants in soil. The innovative nature of this research, which includes coupling chemical, physical and biological studies, will enable researchers to understand the short- and long-term ramifications of the increased use of irrigation with wastewater in agriculture. The proposed research presents an opportunity to recognize and mitigate a major potential threat to long-term sustainable agriculture.

Interactions of engineered nanoparticles with dissolved organic matter (DOM) and organic contaminants in water

PIs: Benny Chefetz and Baoshan Xing (University of Massachusetts, Amherst)


Nanotechnology is one of the world's 21st century most promising new technologies. Engineered nanoparticles have a wide array of applications in industry, personal care and cosmetic products, and biomedical technology. Due to the extensive usage, large quantity of production and disposal, engineered nanoparticles are inevitably released into the environment. These nanoparticles are introduced to agricultural land via irrigation with reclaimed wastewater and/or biosolids applications. Therefore, besides the positive aspects of this new and rapidly growing technology, there are serious concerns over its adverse impacts, among them, health and environmental risks.

We believe that the environmental behaviors of nanoparticles in aqueous systems must be investigated to enhance our understanding of the risk posed by them and to assess their fate in the agro-ecosystem environment. To the best of our knowledge, this will be one of the very first few studies on environmental behavior of nanoparticles in water system in relation to interaction with dissolved organic matter and organic pollutants. This type of study is of high importance since nanoparticles can be released to the environment via disposal and use of reclaimed municipal wastewater and solids where they can interact with dissolved organic matter and organic pollutants.

During the course of this research, we will examine interactions between nanoparticles (ZnO, Ag, and carbon nanotubes) and dissolved organic matter and their influence on contaminant binding. The proposed work will provide fundamental information about the reactivity and interactions of nanoparticles in aqueous systems. In addition, this research is expected to provide valuable data on how nanoparticles affect the fate of organic pollutants because we will study sorption of these pollutants by nanoparticles and nanoparticles complexes with dissolved organic matter. The overall goal of this project is to gain a better understanding of the environmental behavior of engineered nanoparticles with dissolved organic matter and organic pollutants (including pharmaceuticals found in wastewater effluents) in aqueous systems. The scope of this study includes: characterizing various types of engineered nanoparticles and their interaction with dissolved organic matter; and binding studies of organic contaminants by nanoparticles, dissolved organic matter and nanoparticles-dissolved organic matter complexes.

Clay-plant cuticular complexes as natural soil sorbents for organic pollutants

PIs: Benny Chefetz and Tamara Polubesova (Hebrew University)


Plant cuticular residues are important precursors of the soil humus. Cuticular derivatives reconstituted on clays can be considered as a model system of the soil humin, which is an efficient sorbent of organic contaminants. Therefore, to better understand the role of humin and plant cuticular matter as natural sorbents it is essential to study sorption of contaminants to cuticular matter-clay complexes. Limited number of studies of humin sorption properties still leaves open the question about mechanisms of its interactions with contaminants. Physical structure of cuticular matter-clay sorbents is not clarified, and there is scarce information about mechanisms of sorption of organic contaminants by cuticular matter reconstituted on clays.

In this project we plan to reconstitute humin-like materials by loading plant cuticular residues, (cutin, cutan and waxes), on the montmorillonite surfaces (enriched with Na +, Ca2+ and Fe3+) and on soil clay fraction. This will enable us to elucidate the mechanisms of interactions of polar and non-polar xenobiotics by these clay-organic complexes and compare these mechanisms with the xenobiotics-humin interactions. We propose a comprehensive study of structure and properties of cuticular-clay systems and sorption of polar and non-polar organic compounds on these sorbents and humin. We plan to study environmentally relevant polar and non-polar organic pollutants having a wide range of physico-chemical properties. The different molecular structures and physico-chemical properties of selected sorbates will enable us to elucidate mechanisms of interactions of distinct pollutants with cuticular-clay complexes and humin. Surface properties of all cuticular materials, clay-cuticular sorbents and humin will be characterized quantitatively and qualitatively by using elemental analyzer, N2-BET technique, spectroscopic methods (FTIR, NMR), and differential scanning calorimetry (DSC). Spectroscopic and DSC measurements will be performed before and after the sorption, desorption and re-sorption experiments to evaluate changes in physical structure of sorbents. Combination of analytical and spectroscopy methods will provide us with extended information on the changes in properties of cuticular materials due to their binding to clays, and on the surface properties of cuticular-clay sorbents. Comprehensive study of sorption-desorption of contaminants and spectroscopy analyses of the surfaces will provide the elucidation of the mechanisms of sorption behavior of pollutants in cuticular-clay systems with distinct surface properties. The collected detailed information on sorption behavior of organic compounds will help us to better understand the role of humin in the sorption of pollutants and to gain a more penetrating insight into the overall fate of organic pollutants in natural soil and sedimentary environments.

Reclaimed wastewater and sludge as source for pharmaceutical compounds: fate in soil and ground water

PIs: Benny Chefetz and Yitzhak Hadar (Hebrew University), Brian Berkowitz and Ishai Dror (Weizmann Institute of Science)


Pharmaceutical compounds (PCs) occur ubiquitously in reclaimed wastewater used for irrigation of crops in Israel, thus imposing a potential health risk if introduced to the food chain. PCs are also of potential ecotoxicological concern, because they are designed to induce specific biochemical effects and/or they are highly adsorbable, resulting in a tendency to accumulate in solid matter such as soil, sediment and plant tissues. Our major hypothesis is that the fate of PCs in soils and aquifers may be affected principally by the reactivity of the PC and their derivatives in the soil, capillary fringe and aquifer environment, including factors such as interaction with dissolved organic matter or soil/aquifer constituents, as well as sensitivity to microbial modifications. These interactions govern the overall adsorption-desorption processes, uptake and accumulation by plants, biodegradability and mobility of these compounds toward groundwater.

The unique situation in Israel, involving intensive irrigation with treated wastewater since 1985 together with sludge application containing residues and active PCs, provides an excellent opportunity to study the long-term environmental behavior of these compounds in soils. Better understanding of PC transport to and in groundwater, especially across the capillary fringe, together with geochemical interactions, is needed to identify the main processes influencing the fate and occurrence of the active ingredients in the subsurface. So far, only a handful of studies have shown that various PCs may persist in groundwater. Finally, understanding and manipulation of biodegradation processes (mineralization and transformation) will have a major impact on reducing the negative effects of irrigation with treated wastewater contaminated with residual PCs. Due to this gap in information regarding microbial processes affecting the fate of PCs in soil and the intensive irrigation with treated wastewater, another objective of the current study is to elaborate on microbial processes related to biodegradation of PCs.

The result of this effort will be a new, intra-disciplinary understanding of how PCs interact in soils and aquifers - chemically, physically and biologically - under application of reclaimed wastewater and sewage sludge. This is of importance to the emerging field of environment and health risk assessment: it will provide data associated with intensive irrigation of crops using treated wastewater, which might introduce PCs into the food chain. The proposed research presents an opportunity to deal with a potential threat - recognizing and planning for it - before it is too late.

This file last modified 03/07/11